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Unit 1 - Module 1

Lesson 8 – acids and bases

Objectives

Must

Identify acids, bases and alkalis and give the

formula of some common examples.

Could

Define the terms acid, base and alkali.

Should

Construct balanced symbol equations for the

dissolving of acid, bases and alkalis in water and

neutralisation reactions.

Spec statements

1.1.11a1 1 1h1

1a1 explain that an acid releases H+ ions in

aqueous solution;

1b1 state the formulae of the common acids:

hydrochloric, sulfuric and nitric acids;

1c1 state that common bases are metal oxides,

metal hydroxides and ammonia;

1d1 state that an alkali is a soluble base that

releases OH– ions in aqueous solution;

Starter

Using the universal indicator solution, work out

the pH of the common acids and alkalis in the

circus in the lab.

Construct a table before you begin. e.g.Name of substance Formula of

substance

Colour of indicator pH

Hydrochloric acid

Sodium hydroxide

Demo

Rainbow in a jar demonstration 1optional1

Theory - Acids

Definition of an acid 1 A proton donor.

When an acid is added to water, it releases H+

ions 1protons1 into the solution;

E.g. HNO1 1 H+ + NO1-

HHSOH 1 HH+ + SOHH-

The H+ ion is responsible for all acid reactions

that take place and is responsible for the pH of

the solution.

Activity

Learn the definition of an acid and the following

formulae;

1. Sulfuric acid - HHSOH

H. Nitric acid - HNO1

1. Hydrochloric acid - HCl

H. Phosphoric 1V1 acid - H1POH

5. Ethanoic acid - CH1COOH

Theory - Bases

Definition of a base 1 A proton acceptor

Common bases are metal oxides and metal

hydroxides. Ammonia and amines are also

bases.

Bases neutralise acids and have a pH higher

than 7.

Activity

Learn the definition of a base 1and an alkali1 and

the following formulae;

1. Sodium hydroxide - NaOH

H. Calcium hydroxide - Ca1OH1H

1. Magnesium oxide - MgO

H. Ammonia - NH1

5. Potassium hydroxide - KOH

AfL – using whiteboards

Quick test on formulae;

1. Ammonia

H. Potassium hydroxide

1. Sulfuric acid

H. Magnesium oxide

5. Calcium hydroxide

6. Nitric acid

are often called neutralisation reactions as the

pH of the products are neutral.

As well as water a salt is formed in the reaction

when the H+ ion of an acid is replaced by a

metal ion or NHH+.

E.g. Sodium hydroxide reacting with

hydrochloric acid;

NaOH + HCl 1 NaCl + HHO

Looking at the formation of the H products

individually;

Na+ + Cl- 1 NaCl

Here the H+ attached to the Cl- ion is replaced

by Na+ 1a metal ion1

OH- + H+ 1 HHO

This type of reaction can occur between acids

Practical

1. Carry out reactions of acids with metals,

carbonates, bases and alkalis.

H. Use small amounts in test tubes.

1. Record all observation carefully.

For each reaction write a balanced symbol

equation.

1. Recall the four general equations of the

formation of salts from metals, bases, alkalis

and carbonates.

H. Give an example of a balanced symbol

equation for each reaction above.

Write balanced symbol equations for the

following reactions;

1. Magnesium oxide + hydrochloric acid

H. Calcium carbonate + sulfuric acid

1. Potassium hydroxide + nitric acid

H. Ammonia + sulfuric acid

5. Sodium hydroxide + hydrochloric acid

Summary

Identify acids, bases and alkalis and give the

formula of some common examples.

Define the terms acid, base and alkali.

Construct balanced symbol equations for the

dissolving of acid, bases and alkalis in water and

neutralisation reactions.

Extension 1whole extra lesson1

• Determination of the relative atomic mass of a

metal by gas collection.

• For example weigh a sample of lithium and

react with water under a delivery

tube/inverted measuring cylinder and

measure the volume of hydrogen evolved.

• Then titrate solution to determine the

concentration of LiOH.

• Use this value and the volume of gas collected

to calculate Ar